NGC 6981 / C2050-127 / Messier 72 (Updated May 2013) RA: 20:53:27.70 DEC: -12:32:14.3 (J2000) ============================================================ Bytes Format Explanation 1-8 A8 Star ID 10-32 A11,1x,A11 Position 34-35 A2 Units for position R0 denotes RA, DEC in the J2000 coordinates R5 denotes RA, DEC in the 1950 coordinates XA denotes X, Y in arcseconds XP denotes X, Y in pixels 37-44 F8.4 Period (days) 46-51 F6.3 Mean magnitude (or maximum magnitude if "max" is indicated in the remarks column) 53-57 F5.3 Light amplitude (range of variability) 59 A1 Colour for mean magnitude and amplitude e.g. B, V, R, I or P (for photographic). 61-65 A5 Type of variable (draft 2006 GCVS classifications) NV denotes not variable 67-80 A19 Notes and Remarks (f denotes field star) "--" or "----" indicates no data available ========================================================================= ID Position Period ampl C Type Notes/ RA/X Dec/Y Units Remarks ========================================================================= 1 20:53:31.10 -12:33:11.7 R0 0.6198 16.926 0.617 V RR0 2 20:53:34.55 -12:29:02.5 R0 0.4653 -- -- RR0 3 20:53:24.56 -12:33:17.4 R0 0.4976 -- 1.244 V RR0 4 20:53:20.80 -12:31:42.7 R0 0.5525 16.981 0.952 V RR0 5 20:53:25.57 -12:32:41.4 R0 0.5073 16.969 1.197 V RR0 6 20:53:33.19 -12:30:57.7 R0 ---- -- -- NV 7 20:53:27.85 -12:31:19.3 R0 0.5247 17.036 1.067 V RR0 8 20:53:27.57 -12:30:47.8 R0 0.5684 16.966 0.872 V RR0 9 20:53:28.65 -12:31:28.2 R0 0.6029 16.941 -- V RR0 10 20:53:24.84 -12:33:31.3 R0 0.5582 16.971 -- V RR0 Bl 11 20:53:32.03 -12:32:51.3 R0 0.5207 -- 0.881 V RR0 Bl 12 20:53:28.59 -12:32:38.7 R0 0.2879 16.856 0.537 V RR1 13 20:53:28.90 -12:32:02.2 R0 0.5420 -- 1.027 V RR0 14 20:53:27.16 -12:31:42.8 R0 0.6072 16.901 -- V RR0 Bl 15 20:53:23.77 -12:32:39.0 R0 0.5405 16.987 -- V RR0 Bl 16 20:53:27.85 -12:32:37.0 R0 0.5752 16.905 0.831 V RR0 17 20:53:28.22 -12:33:00.0 R0 0.5735 16.968 0.864 V RR0 18 20:53:26.20 -12:32:54.5 R0 0.5356 16.376 -- V RR0 19 20:53:27.98 -12:30:23.5 R0 ---- -- -- NV 20 20:53:24.21 -12:32:03.8 R0 0.5950 16.934 -- V RR0 21 20:53:22.39 -12:32:05.8 R0 0.5312 -- 1.010 V RR0 22 20:53:20.27 -12:32:18.4 R0 ---- -- -- NV 23 20:53:21.14 -12:30:22.1 R0 0.5851 16.948 -- V RR0 Bl 24 20:53:27.16 -12:32:42.0 R0 0.3271 16.861 0.433 V RR1 25 20:53:18.87 -12:31:13.8 R0 0.3533 16.882 0.438 V RR1 26 20:53:21.86 -12:33:04.4 R0 ---- -- -- NV 27 20:53:42.60 -12:36:06.8 R0 0.6738 16.738 0.953 V RR0 DF;Note 28 20:53:32.22 -12:30:56.8 R0 0.5672 16.968 -- V RR0 Bl 29 20:53:25.77 -12:33:11.8 R0 0.5975 -- 0.873 V RR0 30 20:53:32.99 -12:33:52.2 R0 ---- -- -- NV 31 20:53:28.18 -12:31:42.9 R0 0.5423 16.958 0.843 V RR0 Bl 32 20:53:18.82 -12:33:01.4 R0 0.5283 -- -- RR0 Bl 33 20:53:28.18 -12:33:22.1 R0 ---- -- -- NV 34 20:53:27.57 -12:32:10.3 R0 ---- -- -- NV 35 20:53:43.55 -12:31:54.4 R0 0.5438 17.011 0.733 V RR0 DF 36 20:53:27.03 -12:32:16.9 R0 0.5826 16.503 -- V RR0 Bl 37 20:53:28.66 -12:32:24.4 R0 ---- -- -- NV 38 20:53:28.45 -12:32:26.8 R0 ---- -- -- NV? 39 20:53:41.02 -12:28:16.1 R0 ---- -- -- NV 40 20:53:29.19 -12:32:01.6 R0 ---- -- -- NV 41 20:53:28.90 -12:32:38.9 R0 ---- -- -- NV 42 20:53:28.85 -12:32:16.8 R0 ---- -- -- SR? DF 43 20:53:27.36 -12:32:22.4 R0 0.2835 16.939 0.621 V RR1 44 20:53:28.02 -12:32:29.7 R0 ---- -- -- RR0? 45 20:53:28.66 -12:32:20.2 R0 ---- -- -- RR0? 46 20:53:28.97 -12:32:26.5 R0 0.2867 16.806 0.315 V RR1 47 20:53:29.73 -12:32:26.3 R0 0.6491 16.926 0.270 V RR0 48 20:53:26.46 -12:32:27.3 R0 0.6398 16.894 0.465 V RR0 49 20:53:28.27 -12:32:10.9 R0 0.5783 16.937 0.837 V RR0 Bl 50 20:53:28.25 -12:31:58.3 R0 0.4889 16.798 1.136 V RR0 51 20:53:28.41 -12:32:32.3 R0 ---- -- -- RR0? 52 20:53:27.96 -12:32:02.3 R0 ---- -- -- RR 53 20:53:27.00 -12:32:16.7 R0 ---- -- -- RR 54 20:53:28.66 -12:32:02.5 R0 0.0720 18.191 0.246 V SXPhe 55 20:53:24.45 -12:31:27.3 R0 0.0470 19.392 0.174 V SXPhe 56 20:53:28.93 -12:33:05.9 R0 0.0405 19.613 0.087 V SXPhe 57 20:53:27.12 -12:32:13.9 R0 0.334 -- -- RR1 58 20:53:27.38 -12:32:13.3 R0 0.285 -- -- ? ======================================================================= Supplementary Notes and References The RA and dec for V1-42 are from Samus et al. (2009) and for V43-56 are from Bramich et al. (2011). All of the data for V57-58 are from Skottfelt et al. (2013) The most comprehensive study of the variables in M72 is by Bramich et al. (2011) who derived periods with a precision of 6 decimal places. The periods, magnitudes, classifications and Blazhko designations (Bl) listed in the above table are from their study and the amplitudes are from Bramich (2012 - private communication). The only exceptions are the three stars indicated "DF" in the remarks column. For these stars, the data are from Dickens & Flinn (1972, 1973). V27 and V35 were outside of Bramich's field and V42 was saturated in their images. A comparison of the published data for the stars in both studies indicates a difference in scale in the sense that DF's photographic V magnitudes are ~0.1 mag brighter and their V amplitudes are 0.15 to 0.2 mag lower than Bramich's CCD values. ================================================ Notes on individual stars V27: Shapley & Ritchie (1920), Rosino (1953) and Dickens & Flinn (1972) all noted that this star is brighter and has a longer period, high amplitude and greater distance from the cluster centre compared with the other RR Lyrae variables, thus calling into question its membership status. However, it is now considered to be a cluster member. With r ~ 5.2 arcmin, it is well within the tidal radius (~9.2 arcmin) and is considered to be at a more advanced evolutionary state than the other RR Lyrae variables, similar to some of the RR Lyrae in M3 (see Cacciari et al. 2005). V27 was outside the field of view of Bramich et al. ========================================================== Discovery of the variable stars in M72 V1-34 (V6, V19, V33 were supsected variables) discovered by Ritchie and announced by Shapley (1920) with x,y coordinates and an ID chart. Kadla et al. (1995) later showed that V6, V19 and V33 are giant branch stars. V35-41 Sawyer (1953) with x,y coordinates and an ID chart In the course of deriving the RA and dec for V14, V29, V33, V41, Samus et al. (2009) and Kadla et al. (1998) noted that there were errors in the published positions for these variables in earlier versions of our GC variable star catalogues. V42 Dickens & Flinn (1973) noted that they had discovered a new red variable near the cluster centre. The number 42 was assigned and x,y coordinates were listed by Sawyer Hogg (1973) in her 3rd catalog, based on unpublished correspondence with Dickens. V43-V49 = S3, S5, S7, S8, S9, R3, R4 Kadla et al. (1995, 1996) with x,y coordinates in arcsec and an ID chart in the 1996 paper. Approximately 33 of variables V1-42 were also labelled on the ID charts by Kadla et al. (1996). The numbers V43-49 were assigned by Bramich et al. (2011). In their papers, Kadla et al. listed 9 suspected variables (S1-9) and 7 possible RR Lyrae variables (R1-7), all based on their location in the CMD. They did not detect any variations because their study was based on one B frame and one V frame taken simultaneously. With their more extensive data set, Bramich et al. detected variation only in the seven listed here. The others are considered to be non-variable. V50-56 Bramich et al. (2011) with RA, dec and ID charts. They also published RA, dec and ID charts for the other variables they analysed in their study. V57-58 Skottfelt et al. (2013) with RA, dec and an ID chart ------------------------------------------------------------------------- Lynch & Ransom (2011) conducted a search for pulsars, but did not find any in NGC 6981. ======================================================================== References Bramich, D. M., Figuera, J. R., Giridhar, S., Arellano Ferro, A. 2011, MNRAS, 413, 1275 Cacciari, C., Corwin, T. M., Carney, B. W. 2005, AJ, 129, 267 Dickens, R. J. & Flinn, R. 1972, MNRAS, 158, 99 Dickens, R. J. & Flinn, R. 1973, IAU Colloq 21, Var Stars in Globular Clusters and in Related Systems, 82 Kadla, Z. I., Brocato, E., Piersimoni, A., Gerashchenko, A. N., Malakhova, Y. N. 1995, A&A, 302, 723 Kadla, Z. I., Gerashchenko, A. N., Malakhova, Y. N. 1996, IBVS, 4413 Kadla, Z. I., Gerashchenko, A. N., Malakhova, Y. N. 1998, A&A Transactions, 15, 137 Lynch, R. S. & Ransom, S. M. 2011, ApJ, 730, L11 Rosino, L. 1953, Bologna Pub, 6, No. 2, 49 Samus, N. N., Kazarovets, E. V., Pastukhova, E. N., Tsvetkova, T. M., Durlevich, O. V. 2009, PASP, 121, 1378 Sawyer, H. B. 1953, JRASC, 47, 229 Shapley, H. 1920, ApJ, 52, 73 Shapley, H. & Ritchie, M. 1920, ApJ, 52, 232 Skottfelt, J., Bramich, D. M., Figuera Jaimes, R., Jorgensen, U. G., Kains, N., Harpsoe, K. B. W., Liebig, C., Penny, M. T., Alsubai, K. A. et al. 2013, A&A, (in press) = arXiv:1304.2243 ========================================================================